let s=Symbol();// 独一无二
let s2=Symbol();
console.log(s==s2);

let obj={
    a:1,
    [Symbol()]:function(arg){
        console.log('---');
    },
    [Symbol()]:function(arg){
        console.log('+++');
    }
}
// console.log(obj);
for(let key in obj){
    console.log(key);
}
console.log(Object.keys(obj));
console.log(
    Object.getOwnPropertyNames(obj)
)
Object.getOwnPropertySymbols(obj)
    .forEach(item=>{
        obj[item]();
    });
// obj.a
// console.log(obj[s]());
// console.log(obj[s2]());